Choose gypsum cover boards for increased durability

By Georgia-Pacific Building Products. 

Avoid preventable problems in the future when you protect your low-slope commercial projects with gypsum cover boards instead of foam. 

Low-slope commercial rooftops face many challenges over a building's life, including heavy equipment installations, frequent foot traffic and increasingly severe weather conditions. Gypsum board offers superior compressive strength, providing a robust foundation that can withstand these stresses better than a foam cover board like HD ISO.  

DensDeck® Roof Boards by Georgia-Pacific Building Products offer enhanced protection against punctures, fire and wind uplift, making them a more reliable choice for ensuring the longevity of a roofing system. Compared to HD ISO, here’s why you should choose gypsum cover boards: 

1 – Supports your rooftops today and tomorrow 

The landscape of a commercial low slope roof can change a lot over its lifetime. A rooftop will likely endure stress, like HVAC and solar installations, or become a green roof. Weighty rooftop equipment and the foot traffic associated with their maintenance need a solid foundation. When comparing cover board materials like foam-based HD ISO versus a gypsum board like DensDeck® Roof Board, HD ISO cannot provide the rigid support and puncture resistance that glass-mat gypsum can. 

DensDeck® Roof Boards have eight to 11 times greater compressive strength than HD ISO1. Compressive strength (often measured in PSI) measures the amount of force a material can withstand before it cracks or breaks. The higher it is, the better a material will be at resisting punctures, supporting static equipment, and handling the burden of foot traffic. 

“What are you going to ask that roof to do for the next 15 to 20 years? Are you going to add components like HVAC or solar onto it? Or are you going to be in an area where you have really increased negative weather patterns? Applying that long-term asset valuation is critical to deciding what roofing system you should install on your building,” shared Greg Hudson, director of commercial sales for Georgia-Pacific Gypsum. 

Building owners who are mindful about maximizing their asset investment should know about the negative impact that less robust materials can have on the longevity of their roofing systems. And no matter the building type, the roof you install is always protecting something valuable inside. Schools, data centers, hospitals, hotels and warehouses should especially consider the future state of their rooftops, whether it’s a new project or a reroof. 

Plus, by 2028, the U.S. solar industry is expected to triple in size2. The heft of solar installations can damage a roof without adequate support. A solar array requires maintenance, which can increase the threat of puncture damage. A solar array also increases rooftop fire risk simply because it produces electricity. Building owners will have to bear the cost of solar panel removal and reinstallation during reroofing jobs if their roofs and the solar panels have different lifespans. 

Gypsum roof boards are the best option to handle these combined risks. 

“The insulation is typically the most expensive component of a low-slope roofing assembly. When using HD ISO as a cover board, you’re protecting your foam insulation with more foam on top. Yes, HD ISO happens to be 100 PSI compared to 20 PSI for standard polyiso insulation. But our gypsum cover boards start at 900 PSI. If it were my roof, I’d want to protect the insulation with rock, rather than with more foam.” – Ben Williams, Building Envelope Manager at Georgia-Pacific Building Products 

2 – Offers better protection from the elements 

Extreme weather events like severe storms have been increasing across the country since the 1980s3. In addition to enhanced strength that can help resist damage from hail and flying debris, DensDeck® Roof Boards have a strong mat-to-core bond that helps protect against wind uplift during rough weather. They also have a flexural strength range from 100 to 200 LBF (pound-force), compared to the 20 to 40 LBF for HD ISO. 

Flexural strength determines the flex or bending properties of a material. Higher flexural strength can increase a cover board’s flute-span capability while guarding against wind uplift. This helps protect your roof from membrane delamination and fastener withdrawal. HD ISO’s lightweight foam can’t provide the same level of flexural strength and wind-uplift resistance. 

For even more protection against extreme weather, DensDeck® StormX™ Prime Roof Board is FM classified for Very Severe Hail (VSH) in approved single-ply assemblies. Meanwhile, HD ISO is not approved for VSH. 

3 – Goes beyond a Class A fire rating 

One of the most dangerous threats to a commercial low-slope rooftop is the risk of catching fire. Fire can spread quickly from nearby buildings or vegetation — it just takes one burning ember and the right conditions for a roof to catch fire. 

While many roof assemblies are rated as Class A, it is important to know that not all Class A assemblies are the same. Stakeholders need to think beyond fire resistance and consider combustibility when it comes to a cover board. 

DensDeck® Roof Boards are noncombustible per ASTM E136. Their gypsum core and fiberglass mat facers help to stop the spread of fire and mitigate the risk of rooftop damage from every direction. 

DensDeck® Roof Boards also are not chemically treated with fire retardants — gypsum is naturally noncombustible. On the other hand, since HD ISO is made with foam insulation, it is combustible and will smolder and burn under certain conditions. 

Considering the benefits and risks, it’s clear that using anything less than high-performance gypsum roof boards can put your roofing assembly, the building owners’ investment and building inhabitants at risk. 

Need more proof? See how the two cover boards compare in fire tests at DensDeck.com/Risky.  

1 https://www.polyiso.org/page/500SeriesHDCoverBoards *Current specifications as of 1/2024. 

2 https://www.seia.org/research-resources/solar-market-insight-report-q2- 2023#:~:text=Over%20the%20course%20of%20our,of%20year%2Dend%202022 

3 https://www.ncei.noaa.gov/access/billions/ 

Original article source: Georgia-Pacific Building Products